Overview
In almost all of today's computer systems, the image displayed on the screen is stored in a DISPLAY MEMORY, which is also called VIDEO RAM, as in FIG. 1. In DISPLAY MEMORY, there is a memory location for each pixel on the screen. Each memory location can consist of one bit, or several bits. The greater the number of bits for each pixel, the more information can be associated with each pixel. Basically, this information specifies color and brightness of the pixel.
There are numerous different conventions for storing color and brightness information in DISPLAY MEMORY. Computer systems commonly store information as to the red, green, and blue content of each pixel. In contrast, television formats use a different approach.
In general, the television formats, even if their data is in digital format, are incompatible with computer formats. They cannot merely be loaded into a DISPLAY MEMORY in a computer.
For example, in the NTSC system, four bytes of data specify the characteristics of two adjacent pixels. Two of the bytes are used are used to specify color and tint (which are identical for the two adjacent pixels). The two remaining bytes are used to specify intensity, which is different for the two pixels.
This approach reduces the amount of data required, because the color/tint data for the two pixels is transmitted at half the frequency of the intensity data. (This has been found practical because the human eye is less sensitive to color than to intensity.)
The invention seeks to display images of both formats ("computer format" and "television format") on a single computer screen, at the same time. However, the display hardware expects signals following a particular, single format. Thus, for display of dual formats, one format must be translated into another, to attain compatibility with the display.
In the prior art, various external translation systems have been used. These prior art approaches are expensive.